In this review, recent advances in the methods of pre-treatment of plant material for the extraction of secondary metabolites with high biological activity are presented. The correct preparation of ...the material for extraction is as important as the selection of the extraction method. This step should prevent the degradation of bioactive compounds as well as the development of fungi and bacteria. Currently, the methods of preparation are expected to modify the particles of the plant material in such a way that will contribute to the release of bioactive compounds loosely bonded to cell wall polymers. This review presents a wide range of methods of preparing plant material, including drying, freeze-drying, convection drying, microwave vacuum drying, enzymatic processes, and fermentation. The influence of the particular methods on the structure of plant material particles, the level of preserved bioactive compounds, and the possibility of their release during the extraction were highlighted. The plant material pre-treatment techniques used were discussed with respect to the amount of compounds released during extraction as well their application in various industries interested in products with a high content of biologically active compounds, such as the pharmaceutical, cosmetics, and food industries.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The conventional drying technologies presently used in the food industry are hot-air based systems that are normally considered as an energy intensive processes with higher green-house gas emissions ...accounting approximately 15% of the overall manufacturing expenses. The most common drying processes used for the preservation of the food materials are conventional thermal drying, which proved to be a high energy consuming process. With the world progressing towards the application of green technology and sustainable methods, the use of alternative energy efficient drying systems are of paramount importance.
This paper extensively reviewed the energy efficiency and techno-economic performances of a number of non-conventional drying technologies that are currently used in the food industry for drying of the food materials. The reviewed drying technologies include: hybrid systems, heat pumps, super – heated steam, vacuum, microwave, refractance window®, electrotechnologies, ohmic, adsorption mediated and impingement.
It was found that the hybrid drying systems with the solar drying input and refractance window® drying were among the most promising energy efficient drying methods that could be potentially used for drying of the food materials in industrial processes.
•Drying technologies are very important unit operations for removing moisture content of food materials.•They facilitate long-term storage, prevention from microbial contamination and other detrimental chemical reactions.•Most of the drying methods are highly energy intensive and use fossil fuels as energy sources.•This paper reports that the most promising energy efficient technologies are hybrid and pump drying systems.•The new generation of the drying technologies should demonstrate improved dry product quality and sustainability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of three different drying methods (hot-air, combined hot-air-microwave, and vacuum-freeze) on the sensorial, textural, nutritional, and other quality characteristics of persimmon chips was ...compared. The result showed that the freeze-dried chips had the best nutritional and quality features. However, persimmon chips processed by combined hot-air-microwave and freeze-techniques had the same sensory score (85.40 points), which were higher than that of hot-air dried samples (70.51 points). Additionally, persimmon chips dried with aid of hot-air technique had the lowest chewability value and hardly met the panelists' requirements. These disadvantages could be avoided by using a combined hot-air-microwave drying method with lower power consumption compared with the others. The optimized combining microwave and hot-air drying conditions were as follows: 1 mm thickness of persimmon slice, a temperature of 70 °C at an air velocity of 1.0 m/s of initial hot-air drying system until the moisture content of persimmon samples reached 10% (about 150–160 min) and 10.7 Wg−1 of the following microwave-drying system. It was concluded that the combined hot-air-microwave drying technique could be used for processing persimmon chips with high quality and nutritional values as well as low operating costs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Evaluation of solar dryers' standards and their applications were reviewed.•Different types of solar dryers can be obtained relying on the individual circumstances.•Practical and economic ...potentialities are indispensable to ease the application of solar dryers.•The CO2 emission was significantly mitigated by employing solar drying.•PCMs keep the drying chamber at 11 °C higher than ambient during sun-off hours.
Dried foods, especially fruits, have become a requirement of many fields in most societies not limited only to developing countries that often preserve food for periods of drought. Consequently, there has become a development in the concept of dried foods for many people, and this is reflected in the methods of producing and drying fruits, in particular, there is rapid development in the methods of production and manufacturing, it has recently become a prevailing trend in the whole world on the necessity of limiting and saving in non-renewable energy. The current work presents and discusses some efforts in developing agricultural product drying processes. Solar drying and other methods, spray drying, freeze-drying, Refractance Window, and microwave drying, as well as several pre-treatment techniques, were assessed in terms of performance, product quality, and economic feasibility. Furthermore, the solar drying methods have been classified based on the solar dryer type into, absorber plate solar collector-based dryers, tube solar collector heater-based dryers, and solar dryers with thermal storage. Accordingly, a CO2 reduction of 135.04 tons was indicated by utilizing an evacuated tube solar heater for drying ginger.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The smell of food is one of the most important factors in assessing its quality. In this study, the influence of drying method on aroma/volatile compounds of oyster mushrooms (Pleurotus ostreatus ...Jacq.) was evaluated. The drying methods tested were convective drying (CD), freeze-drying (FD), vacuum microwave drying (VMD), and a combination of convective predrying and VM finish drying (CPD-VMFD). The volatile compounds were extracted by solid-phase microextraction and identified by gas chromatography-mass spectrometry. The best fitting model to describe the drying kinetics of the oyster mushroom was Henderson and Pabis model. Thirty-four volatiles in fresh oyster mushrooms were identified, with 3-octanone (2,890 µg/100 g dry basis) and 3-octanol (991 µg/100 g) being the major components. The total concentration of volatiles of fresh mushroom (4,506 µg/100 g) was drastically reduced by all drying treatments, although the highest contents were found after: (i) CPD (50°C)-VMFD (480 W) (245 µg/100 g) and (ii) VMD at 480 W (143 µg/100 g). According to the sensory data, the products dried using the treatment CPD (50°C)-VMFD (480 W) were those closer to the fresh mushrooms.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Medium and short-wave infrared drying (MSWID) is a new drying technology, widely used for drying agricultural products, such as fruits, vegetables, and edible fungi. MSWID is superior to conventional ...drying technologies due to its high energy efficiency, uniform heating, and high product quality. This method can be combined with other drying techniques to improve the penetration degree, drying rate, and product quality, including vacuum freeze-drying, differential pressure flash, air impingement, and microwave vacuum drying. This review comprehensively investigates and discusses the principles, characteristics, and applications of MSWID with/without other techniques for agricultural products. The effects of three parameters (drying temperature, radiation power, and distance) on the drying kinetics and product quality are discussed in detail. The combination of MSWID with other drying methods is also summarized, providing new insights into MSWID applications.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
This comprehensive summary of the state of the art and the ideas behind the reaction engineering approach (REA) to drying processes is an ideal resource for researchers, academics and industry ...practitioners. Starting with the formulation, modelling and applications of the lumped-REA, it goes on to detail the use of the REA to describe local evaporation and condensation, and its coupling with equations of conservation of heat and mass transfer, called the spatial-REA, to model non-equilibrium multiphase drying. Finally, it summarises other established drying models, discussing their features, limitations and comparisons with the REA. Application examples featured throughout help fine-tune the models and implement them for process design and the evaluation of existing drying processes and product quality during drying. Further uses of the principles of REA are demonstrated, including computational fluid dynamics-based modelling, and further expanded to model other simultaneous heat and mass transfer processes.
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